Nickel clad ferrous article



Patented July 14, 1942 UNITED STATE s PATENT OFFICE NICKEL cum masons Aa'rrcmi Andrew Wesley, Plainfleld, and Harry Rollason Copson, Cranford, N. 3., assignors to The International Nickel Company, Inc., New N. Y., a corporation of Delaware York,

No Drawing. Application September 23, 1940, Serial No. 357,990. In Canada August 7, 1940 3 Claims.

by which ferrous articles particularly sheets, bars and strips of steel or the like may be provided with a corrosion resistant ornamental and decorative surface. It also has been proposed that iron or steel billets be coated with nickel by electrodeposition before rolling, forging and heat treating in order to reduce or eliminate the corrosion or formation of scale accompanying these operations when unclad ferrous billets are employed. In fact, many processes have been proposed whereby ferrous articles either in, the early stages of fabrication or in the substantial finished condition have been provided with a corrosion resistant skin or coating. However, none of'these proposed processes have been entirely satisfactory either from an economic standpoint or because of technical drawbacks or deficiencies. It has always been the aim of iron and steel manufacturers to reduce their costs to the lowest possible minimum communsul'ate with quality production. Consequently, while in the past it has 'been possible to provide satisfactory coatings of nickel or iron and steel bases, the time and the cost of nickel plating ferrous bases has been such as to preclude nickel plating of many ferrous articles.

Another problem not entirely connected with the nickel plating of ferrous articlesarises in the production of galvanized sheet. While for many uses galvanized sheet is an ecomonlc product, for other purposes the cost'cf hot dipping to produce galvanized sheet has been such as to seriously impede its competition with other materlals. In the tin plating field likewise an economic problem has arisen in the production of tin plate. Hot dipped tin plate is in many respects satisfactory from a technical standpoint.

However, in the production of tin plate by the electrodeposition of the tin coating lighter or thinner coatings of tin are deposited and under these circumstances the corrosion resistant properties of the base become important. Thus,

electroplated tin plate is said have one fundamental weakness which surrounds the soldering in making tin cans. The soldering of electro tin plate results in poor adhesion of the tin to the steel and as a result electro tin plate is only satisfactory for dry packing whereas hot dipped tin is useful for all purposes in the can industry.

' .It is recognized that a nickel coated ferrous article may be used as a base upon which tin may be electrodepositcd to produce an electro tin plate and that'such electro tin plate gives satisfactory results; However, the cost of the usual methods of providing ferrous sheet with a nickel coating 5 eliminates an electro tin sheet having an inter- I mediate layer of nickel or nickel alloy interposed between the ferrous base and the tin coating. It has been discovered that an entirely satisfactory coating for ferrous articles, such as sheet,

strip and the like, can be obtained and this coating is entirely satisfactory not only from a technical standpoint but also from an economic view.

It is also possible by employing the principles of the present invention to produce a nickel coated article which gives satisfactory performance, has

a satisfactory appearance and is substantially equivalent to ferrous articles having an electrodcposited nickel plate of the same thickness.

It is an object of the present invention to proso vide a means for coating ferrous articles and particularly ferrousarticles of the class known as mild steel with-a corrosion resistant decorative and/or ornamental coating of nickel.

It is another object of the present invention to as provide a process for producing nickel clad ferrous articles which may be introduced into the production line of a sheet mfll without seriously hampering the conventional speed of pr uction. t

It is a further object of the present invention to provide a means for producing nickel clad ferrous articles wherein the nickel is deposited upon the base element inthe form of a suspension or paint.

The present invention also contemplates the use of nickel in the form of a powder having a particular shape, a particular degree of fineness and other critical characteristics and suspended 'in a vehicle having certain critical character- 4o istics. Y

It is also within the contemplation of the present invention to provide a means for producing nickel coated ferrous articles wherein the initial painted surface is compacted and made more 4 homogeneous by cold rolling.

Other objects and advantages will become apparent from the following description:

In a general way experts in the art have appreciated for some time that from an economic vso standpoint the nickel cladding of ferrous article's could be improved. That is to say, in the production of nickel plated ordinary steel prior art processes did not provide a completely satisfactory economic solution to the problem. The exports in the art also appreciated that it was deslrable to develop or discover a. means whereby ,mild steel articles such as sheets,stripsand the like could be provided with a nickel coating subi stantially equivalent to an electrodeposited nickel coating of similar thickness which could be mthe results are now entirely satisfactory from.

a technical standpoint, from a cost standpoint these nickel plated articles sufier economically in competition :withrother clad metals- It has also been proposed to produce nickel clad sheets,strips, etc. by clamping slabs of nickel to slabs of iron or steel and then makingthe twosheets integral by hot rolling and annealing. This likewise gives satisfactory results from a technical standpoint but from an economic standpoint can not compete with other thinly clad articles. a long investigation in which many factors had to be considered'and in which, the solutions to various incidental problems had to be found, it was finally discovered that sheets of mild steel for examplecould be provided with a nickel coating as free from porosity as the best electrodeposited plate of the same thickness. In the past attempts have beenmade to nickel coat such After material by spreadingnickel powder onthe surface of a sheet of steel or other ferrous metal and then subjecting the, steel sheet and its superimposed powder layer to sintering tempera turesfollowed by hot and/or cold working. At-

t tempts havealso been made in which the sintering and working operationswere repeated sev-' eral times. However, such investigations resulted in failure.

' It was then proposed to use nickel powder such as that produced by the carbonyl process or by an electrolytic process suspended in 9. ve-

hicle such as a nitrocellulose lacquer or collodion. After coating the ferrous basewith this nickel lacquer the coated sheet was then subjected to sintering temperatures and the sinv tered sheet subjected to hot working. Variations of this process included rolling before sintering as well as rolling after sintering. While a nickel plated article thus could be obtained the porosity of the coating was excessive and it was also found that many blisters were produced. on opening these blisters it was found that in most cases the underlying ferrous surface had a coating of oxide. Consequently this process was very unsatisfactory.

Aftermany attempts had been made to develop or discover a satisfactory process based upon the application of nickel in a powder form, as a paint, it was found that many variables had to be controlled in order to produce satisfactory results. For example, the shape of the particles of the nickel powder plays an important role in the process. The composition of the vehicle in which the nickel powder is suspended for application to the ferrous base is a factor. The volatility of the diluent of the vehicle likewise must be considered, and the order in which the steps of sintering and rolling together with the amount of reduction in thickness of the painted article must likewise be controlled within relatively narrow limits. When all these problems satisfactory'results, but it has, been found that nickel powder in which the preponderant por-- had been solved a process had been discovered which gave satisfactory results.

Broadly stated; the process of the present invention involves suspending nickel powder, the particles of which have a preferred shape in a vehicle having a critical composition, a critical viscosity and a. critical volatility or rate of evaporation. It is preferred to treat the particles and/or choose the vehicle so that leafingof the particles results. The process of the present invention also involves sintering or heating the painted article in a controlled atmosphere followed by cold working within critical limits and, in its simplest embodiment, followed by a second heat treatment and a second cold working. The nickel powder suspended in a suitable vehicle may be painted on the ferrous base With a brush or deposited :thereonbyspraying. It has been found that the simplest method of applying the nickel coating is byspraying, since applying the nickel varnish'with a brush in the hands of unskilled or careless operators results in the for mation of brush marks which result. in unsatisfactoryporosity of the final nickelco ating. The

viscosity of the varnish likewise must be taken into consideration-and it has been found that a varnish constituted or comprising about by volume varnish meeting the requirements of the U. S. Federal specification No. TIY-V-l2lc and 1%; by volume mineral spirits is a most satisfactory vehicle for the nickel powder although for metallurgical reasons a varnish of the same consistency. but free from lead dryerswould be more desirable. Nickel powder in which mostof the particles are of spherical shape has given untion of the particles or practically all of the particles are in the form of thin flakes, provides most satisfactory results. It has also been discovered that the amount of nickel powder suspended in a unit of vehicle is an important factor in obtaining the most satisfactory results. That is, whereas one might assume that the more powder suspended in a unit of vehicle the better would 'be the quality and character of the coat ing, it has been discovered that such is not the case. The amount of nickel suspended ma unitvolume of varnish vehicle must be controlled within critical Furthermore, the nickel lacquer or varnish must be applied at a carefully controlled rate based upon the amount of nickel applied to a unit of surface. It is also advantageous to employ a vehiclewhich enables or which tends to cause the nickel flakes to lie upon the surface of the base element much as the scales of a fish are arranged herein referred to as leafing. The incorporation of a. small amount, say about 1% to about 3% of such materials as aluminum stearate and the like during the grinding of the flake improves this tendency, and makes it possible for the sheets or leaves of nickel powder to orient themselves with respect to the base element in a for-- mation which may be called scale-like. The advantage of such orientation will become aphaving a leaf or sheet or scale-like shape when laid upon a base element in a scale-like formation present an enormously greater number of points of contact not only with each other but also and enhances with the underlying base than do particles having a spherical shape such as the particles of previously available commercial nickel powders. After the nickel varnish has been applied to rams of nickel flake.

2,289,614 the ferrous base element, the varnished article is heat-treated in a non-oxidizing atmosphere for a period of time dependent upon the temperature. The temperature of the furnace may be between 1400" F. and 2100 F. and preferably is maintained at a temperature of about 1800 F. Heat treatment of the varnished article at 1800 F. for 1 hour has been found to be sufficient. This heat treatment is carried out in a non-oxidizing atmosphere, preferably in hydrogen and completely eliminates organic material from the coating. After the heat treatment the heat treated article is then cold rolled to about 20% reduction. Subsequent to this cold rolling the rolled heat treated article is then subjected toa second sintering or heat treatment at the same or other temperatures within the temperature range and preferably at about 1800 F. p

The time of heat treatment in this second heat treatment likewise is dependent upon the temperature and it has been found that 1 hour at 1800 in an atmosphere of hydrogen is preferred. Of course in the second heat treatment as in the first a non-oxidizing atmosphere is maintained. After the second heat treatment, if a bright finish is desired, the coated article may again becold rolled to about 10% reduction. Nickel coatings having a thickness of about 0.0001 to about 0.001 inch thickness have been produced by employing the principles of the present invention.

I order that those skilled in the art shall have a better understanding of the present invention, the steps of the process and the novel combination of operations will be described in conjunction with the production of nickel clad mild steel as an illustrative example. A sheet of 17 to 27 grams of varnish per square foot corresponding to about 0.0004 .to about 0.0006 inch,

of compact nickel. The varnish is prepared by diluting 10 to parts by volume of varnish such as that which meets the requirements of the U. S. Federal specification No. IT-V4211: with 90 to 80 parts by volume of mineral spirits. Nickel welding or sinterlng of the nickel flakes. When the cold working has resulted only in a reduction of about 10% it is preferred to cold roll the twice heat treated article to bring about a further 10% reduction which produces a superior appearance. It is important to note that the initial heat treatment is carried out at a temperature at which practically all the varnish and diluent are driven oil. from the painted article. Whether this be by evaporation or decomposition appears to be immaterial althoughthe residue should be a minimum while the rate at which the varnish or the products of the decomposition thereof escape has an important efiect upon the porosity of the final plate.

The'cold' rolling not only compacts the nickel coating and causes a certain amount of flow of the nickel particles but in addition provides a polished or bright surface which is desirable in many instances for its decorative effect.

When desirable the heat treatment may be carried out at temperatures at which there is an interdiflusion of the nickel and the surface layers of the ferrous base element. By such interdiffusion a term nickel alloy is produced.

Although the present invention has been described in conjunction with a preferred embodiment thereof, those skilled in the art will readily .appreciate that variations and modifications can be made. It is to be understood that such variations and modifications are to be considered within the purview of the specification and the scope of the appended claims. Thus, while only one varnish has been described in conjunction with the present description, those skilled in the art will readily appreciate that there are many varnishes meeting 'these requirements. While the particle size of the nickel flakes has not been set forth, powder in which practically all of the particles pass a 325-mesh screen has given satisfactory results, particularly when the particles were in flake form. The time of heat treatment may be varied from about 1 hour to about 16 hours and the temperature varied from-1400 to 2100 F. Very good results have also been obtained by carrying out the first heat treating operation at 1400 F. for about 1 hour and the flake powder is then incorporated in this varnish to the extent of about 50 to 80 grams of nickel flake per 100 cc. of diluted varnish. It is preferred however to compound the nickel varnish by mixing 10 parts by volume of varnish and 90 parts by volume of kerosene and suspending in each 100 cc. of the aforesaid varnish about 80 The varnished sheet is then heat treated for about 1 hour at about 1800 I". in an atmosphere of hydrogen. As a result of this heat treatment all of the vehicle of the the leaves of nickel is substantially not disrupted Subsequent to this first heat treatment step, the heat treated coated article is subjected. to cold rolling. Preferably the cold rolling is carried out until a 20% reduction has resulted, although the cold working may be 10% to 25% reduction in this first cold workingstep. After the cold rolling step has been completed the cold rolled article is subjected to a second heat treatment preferably at about 1800 F. for one hour in an atmosphere of hydrogen, which effects a further varnish is evaporated or volatilized or decomposed at such a rate that the scale-like deposition of.

second heat treating operation at 1800 F. for

about 1 hour.

It is also to be noted that this new process permits the nickel coating to be applied locally,

for example on one side of a sheet or strip of steel, which permits further economies. The process may also be employed for coating iron or steel-strip used for radio tube parts where certain parts are coated with a carbonaceous layer applied over the nickel layer by any of the well known processes.

Furthermore, when desirable, thick coatings may be obtained by a repetition of the steps of the process of the present invention. For example, a cleaned sheet of metal may be sprayed with the special nickel paint, sintered, rolled, sprayed again, sintered and rolled again and the aforedescribed operations repeated. After spraying, sintering and rolling the metal sheet, the rolled article may be rolled again when desirable.

We claim:

l. A process for producing nickel coated fer-' rous articles which comprises applying a varnish comprising 10 to 20 parts byvolume of varnish meeting the requirements of U. S. Federal specification No. TT-V-12la and to 80 parts by volume of mineral spirits and containing 50 to 80 grams of nickel flakes per cc. of varnish to a surface of a ferrous article to obtain a coated jecting said cold rolled article to a second heat.

treatment in a non-oxidizing atmosphere at a temperature of about 1400 to about 2100 F. for a period of time depending upon the temperature whereby a nickel coated ferrous article is obtained having a nickel surface of suitable impermeability.

2. A process for producing nickel coated ferrous articles which comprises spraying a nickel varnish on a horizontal surface of a ferrous article at a-rate of about 17 to about 27 grams per square foot to obtain a coated article having a porous surface, said varnish consisting of parts by volume of varnish meeting the requirements of U. S. Federal specification No.

T-V-12la, and 90 parts by volume of mineral spirits and containing 80 grams of nickel flake per 100 cc. of varnish, subjecting said coated article'having a porous surface to heat treatment at a temperature of about 1400 F, for about one hour in an atmosphere of hydrogen to obtain a heat treated coated article, subjecting said heat a reduction of about 10%- to obtain a cold rolled coated article, subjecting said cold rolled coated article to heat treatment at 1800 F. for about one hour in an atmosphere of hydrogen to obtain a twice heat treated coated article and subjecting said twice heat treated coated article to cold rolling to obtain a further 10% reduction whereby the porosity of said surface layer is reduced 10 to a practical minimum.

3. A process for producing nickel coated ferrous articles which comprises applying a varnish consisting of 10 parts by volume of varnish meeting the requirements of U. S. Federal specification 'IT-V-lZla parts by volume mineral spirits and 80 grams of nickel flake per cc. of varnish and mineral spirits to a surface of a ferrous article to obtain a coated article having a porous'surface, subjecting said coated article having a porous surface to heat treatment at a temperature of about 1800 F. in an atmosphere of hydrogen for about one hour to obtain a heat treated article having a porous surface, cold rolling said heat treated article to obtain a reduction of about 20% to producers, cold rolled heat treated article, subjecting said cold rolled article to heat treatment at a temperature of about 1800 F. for about one hour in an atmosphere of hydrogen and subjecting said heat treated cold rolled article to a second cold rolling to obtain a further reduction of about 10% whereby the porosity of the surface layer of said coated article is reduced to a practical minimum.

ANDREW WESLEY.

HARRY ROLLASON COPSON. 

